The present invention relates to a photosensitive recording material with a layer base and a photosensitive layer, which essentially contains a diazonium salt polycondensation product, a binder which is insoluble in water and soluble or at least swellable in organic solutions or aqueous alkaline solutions, a polymerization initiator which forms radicals when exposed to actinic radiation and a polymerizable olefinically unsaturated compound containing at least one unsaturated group and having a boiling point at normal pressure of over 100.degree. C. The copying material prepared therefrom is mainly suitable for the preparation of lithographic plates of high quality.
It is known that the lithographic and printing properties of photosensitive mixtures can be effected by suitable combinations of photosensitive layers of different composition.
Thus, for example, U.S. Pat. No. 3,905,815 describes a photosensitive recording material which on a suitable base material, has first a very thin layer of a diazonium salt compound and on top thereof, a layer of a photopolymerizable compound. The resolving power of the recording material is claimed to be improved by this combination.
A similar combination is proposed in German Offenlegungsschrift No. 2,843,762. In this case a diazonium salt polycondensation compound which is water-soluble and is intended to act as a hydrophilizing intermediate layer on the base at the same time is used as lower layer. Here, too, an improvement of the resolving power and also an improved storage stability are described.
From the German Offenlegungsschriften No. 2,024,244, 3,130,987, 3,036,077 and 3,404,366, photosensitive mixtures (albeit as monolayers) are known which are composed of the combination of a diazonium salt polycondensation product with a polymeric binder which is soluble in aqueous alkaline developers or at least swellable. Such mixtures exhibit very good lithographic properties, but, in addition to certain specific disadvantages, have the general and therefore decisive disadvantage that their photosensitivity and, in particular, the development capability decreases drastically at fairly high layer thicknesses so that such layers are, in general, suitable only for medium print runs. In addition, the more difficult development capability results in an increased consumption of developer.
From the German Offenlegungsschriften No. 2,361,931, 2,903,270, 3,007,212, 3,425,328 and the German patent application with the application number P 3,528,309.2, photosensitive recording materials are known whose photosensitive layer contains a diazonium salt polycondensation product, a polymerizable compound, a photoinitiator and a polymeric binder. An improved resolution, increased print runs and fast aqueous alkaline development capability are mentioned as advantages of this combination. A disadvantage of these mixtures is, however, their limited storage stability.